Multi-module bidirectional zero voltage switching DC-DC converter

Abstract

A multi-module bidirectional power converter may comprise a low side common node, a high side common node and at least first and second bidirectional DC/DC converter modules. The modules may comprise first and second low voltage switches, first and second high voltage switches and a transformer. The transformer may comprise a low side winding having first and second legs and a high side winding having first and second legs. The first leg of the low side winding may be connected with the first and second low voltage switches of the module. The second leg of the low side winding may be connected with the low side common node of the multi-module bidirectional power converter. The first leg of the high side winding may be connected with the first and second high voltage switches of the module. The second leg of the high side winding may be connected to the high side common node of the multi-module bidirectional power converter. Such an arrangement may provide operability of the multi-module bidirectional power converter with any one or more of the modules so that efficiency is maintained when electrical loads are high and so that Zero Voltage Switching is maintained when electrical loads are low.

1. A multi-module bidirectional power converter operable in a multi-module mode and in a single module mode comprising:
 a low side common node; 
 a high side common node; 
 at least a first and a second bidirectional DC/DC converter module each comprising:
 first and second low voltage switches; 
 first and second high voltage switches; 
 a transformer comprising;
 a low side winding having first and second legs; and 
 a high side winding having first and second legs; 
 
 
 wherein, as to each of the at least first and second bidirectional DC/DC converter modules, the first leg of the low side winding is connected with the first and second low voltage switches of the module; 
 wherein the second leg of the low side winding is connected with the low side common node of the multi-module bidirectional power converter; 
 wherein, as to each of the at least first and second bidirectional DC/DC converter modules, the first leg of the high side winding is connected with the first and second high voltage switches of the module; and 
 wherein the second leg of the high side winding is connected to the high side common node of the multi-module bidirectional power converter; and 
 whereby the multi-module bidirectional power converter is operable with any one or more of the modules so that efficiency is maintained when electrical loads are high and so that Zero Voltage Switching is maintained when electrical loads are low. 
 
     
     
       2. The multi-module bidirectional power converter of  claim 1  further comprising:
 a low side DC bus connected to first sides of the low voltage switches of the at least first and second converter modules; 
 an auxiliary DC bus connected to second sides of the low voltage switches of the at least first and second converter modules; and 
 wherein the at least first and second converter modules comprise an inductor interposed between the second sides of the low voltage switches of the converter module and the DC bus. 
 
     
     
       3. The multi-module bidirectional power converter of  claim 2  further comprising:
 two low-side splitting capacitors; 
 wherein the low-side splitting capacitors are interposed between the second sides of the low voltage switches; and 
 wherein the low side common node is connected to the auxiliary DC bus at a point that is between the two low-side splitting capacitors, whereby the two low-side splitting capacitors are commonly operative for all of the power converter modules. 
 
     
     
       4. The multi-module bidirectional power converter of  claim 1  further comprising:
 a gating controller; and 
 wherein the gating controller produces gating signals that produce successive operation of each of the power converter modules with a phase shift relative to other ones of the power converter modules. 
 
     
     
       5. The multi-module bidirectional power converter of  claim 4  wherein the gating controller produces gating signals that are the same for all of the power converter modules except for the phase shift. 
     
     
       6. The multi-module bidirectional power converter of  claim 5  wherein the gating controller produces gating signals that are phase shifted in accordance with the relationship 2 π/n where n is the number of converter modules in the multi-module bidirectional power converter. 
     
     
       7. The multi-module bidirectional power converter of  claim 1  further comprising a shunt auxiliary inductor in at least one of the converter modules. 
     
     
       8. A multi-module bipolar bidirectional power converter operable with one or more of its modules comprising:
 a gating controller connected to control gating for any one or more power converter modules; 
 a bipolar low side DC bus having a positive rail, a negative rail and a neutral point; 
 a bipolar high side DC bus having a positive rail, a negative rail and a neutral point; 
 at least a first and second ones of the power converter modules, comprising:
 a first low voltage switch having a first side connected to the positive rail of the bipolar low side DC bus; 
 a second low voltage switch having a first side connected to the negative rail of the bipolar low side DC bus; 
 the first and second low voltage switches having second sides that are connected together; 
 an inductor interposed between the low side DC bus neutral point and the second sides of the first and second low voltage switches; 
 a low side winding of a transformer having a first leg connected to the inductor and having a second leg connected to the neutral point of the low side DC bus; 
 a first high voltage switch having a first side connected to the positive rail of the bipolar high side DC bus; 
 a second high voltage switch having a first side connected to the negative rail of the bipolar high side DC bus; 
 the first and second high voltage switches having second sides that are connected together; and 
 a high side winding of the transformer having a first leg connected to the second sides of the first and second high voltage switching devices and having a second leg connected a neutral point of the high side DC bus. 
 
 
     
     
       9. The multi-module bipolar bidirectional power converter of  claim 8  further comprising a low side blocking capacitor interposed between the second leg of the low side winding of the transformer and the neutral point of the low side DC bus. 
     
     
       10. The multi-module bipolar bidirectional power converter of  claim 8  further comprising a high side blocking capacitor interposed between the second leg of the high side winding of the transformer and the neutral point of the high side DC bus. 
     
     
       11. The multi-module bipolar bidirectional power converter of  claim 8  further comprising:
 first and a second highside splitting capacitors; 
 wherein the first highside splitting capacitor is interposed between the neutral point and the positive rail of the high side DC bus; 
 wherein the second highside splitting capacitor is interposed between the neutral point and the negative rail of the high side DC bus; and 
 wherein the two highside splitting capacitors are commonly operative for all of the power converter modules. 
 
     
     
       12. The multi-module bipolar bidirectional power converter of  claim 8  wherein the gating controller produces gating signals that produce operation of each of the power converter modules with a duty cycle of 50%. 
     
     
       13. The multi-module bidirectional power converter of  claim 8  wherein the gating controller produces gating signals that are the same for all of the power converter modules except for phase shift. 
     
     
       14. The multi-module bidirectional power converter of  claim 8  further comprising a shunt auxiliary inductance on at least one of the power converter modules. 
     
     
       15. The multi-module bidirectional power converter of  claim 8  wherein the low side of the converter does not have splitting capacitors. 
     
     
       16. A method for bidirectional conversion of power comprising the steps of:
 converting power through a plurality of interconnected power conversion modules operated in succession; 
 employing a phase shifting gating pattern so that each module is operated with a phase shift relative to a prior module of the succession and a phase shift relative to a subsequent module in the succession; 
 determining a load level for the plurality of conversion modules; 
 comparing the determined load level against a predetermined low-load condition at which the plurality of conversion modules will not operate with zero voltage switching (ZVS); and 
 changing the gating pattern so that only a single one of the conversion modules operates during the low load condition, whereby the converter continues to operate with ZVS. 
 
     
     
       17. The method of  claim 16  wherein the step of employing a phase shifting gating pattern is performed so that the phase shifts between the modules are equal. 
     
     
       18. The method of  claim 17  wherein the step of employing a phase shifting gating pattern is performed so that the phase shifts between the modules is 2 π/n, where n is the number of modules. 
     
     
       19. The method of  claim 16  further comprising the step of passing current though an auxiliary shunt inductor.